CHOICE

Carbon case

SUSTAINABILITY

Refurbish or build new? The carbon case

Across the world, waves of new tall building development are creating some competition with their forerunners. Increasingly, older buildings can risk becoming stranded assets – outdated, expensive to maintain, and not offering what modern occupiers require in terms of specification or sustainability criteria. Decisions must be made.

Completely new buildings can offer some greater economic and public benefits over refurbishing an existing structure, as well as advantages of lower operational cost and carbon if delivered to the right specification.

However, many regions around the world, from Canada to Australia, are looking to reduce the level of demolition and rebuild if there is a viable retrofitting option. The ultimate objective is to lower how much embodied carbon is generated by new development. Carbon is becoming a deciding factor.

For example, the City of Westminster in London and its proposed Policy 43 Retrofit First, which aims to promote and accelerate the retrofitting of existing buildings (regardless of height). Similarly, the December 2025 City of London Carbon Options Guidance contains revised criteria for which projects must undertake carbon option studies, now based on the retention of at least 50 percent of the superstructure by area. By assessing the carbon case based on London’s example, we can better advise decision-makers on similar choices, wherever in the world new projects may be planned.

EMBODIED CARBON

Carbon saving by default

Simply put, refurbishing existing high‑rise buildings preserves the substantial embodied carbon already invested in the original structure.

The frame, foundations and core elements of high‑rise buildings account for most embodied emissions – often 50 to 70 percent of a building’s total lifecycle carbon.

Refurbishment retains these and avoids the carbon‑intensive processes of producing new steel, concrete and façade systems. There is also an added cost factor linked to this in the UK, as all these components (if imported) will be subject to a new carbon tax from 2027.

The default embodied carbon saving of refurbishment can represent several hundred kilograms of carbon emissions per metres squared (kgCO2e/m2) when compared to a full redevelopment. There is naturally a sliding scale based on the level of intervention in refurbishment. Altering the existing structure, increasing building height, adding atria or expanding floor plates will also increase the amount of embodied carbon.

At Turner & Townsend our Embodied Carbon Calculator (ECC) tool helps clients understand the embodied carbon impact of their projects and helps navigate the embodied carbon question of new v. refurbishment.

The ECC allows us to manage and control the dual currencies of construction – carbon and cost – side by side to allow insightful decision making to achieve the optimum balance of meeting sustainability targets and developing a financially viable solution.

ANALYSIS

Comparing the data

Turner & Townsend has drawn together a data-led study to more accurately interrogate how the embodied carbon of refurbished and new build tall towers compare. We used the average embodied carbon assessed using our proprietary Embodied Carbon Calculator (ECC) on three 25-35 storey new build tall buildings in London.

The carbon comparison is quite stark:

A refurbished office is over 500kgCO2e/m2 lower than the benchmark new build – largely driven by carbon savings on the substructure and superstructure.
Using low carbon concrete and structural steel alternatives on a new build saves around 150kgCO2e/m2 from the overall upfront embodied carbon total.
Meeting the 700kgCO2e/m2 set in the draft UK Net Zero Carbon Building Standard for 2026 is incredibly challenging for a new build tower, and will become even more so as the proposed targets reduce each year.

The data and our experience in the London Market suggests there will be a shift towards refurbishment of tall buildings. We hope this will lead to an exciting period where design teams find innovative ways to achieve the economic and public benefits of new build while dealing with existing frames and grids, even if they do not align with current market norms of floor to ceiling height and column spacing.

The circular economy also has a key role to play – arguably as much as low carbon materials and design efficiency. The re-use of reclaimed structural steel in structures and recycled glass and aluminium in façades has the potential to reduce embodied carbon significantly on new build projects. However, it requires forward planning to source the materials from donor buildings or via material trading platforms.